- C³ Command, control and communications.
- CAA Civil Aviation Authority (UK).
- cabane Structure, usually of braced struts, to support load above fuselage or wing. May carry parasol wing, engine nacelle or upper wing of most biplanes.
- cabin altitude Height above S/L at which ambient pressure is same as inside cabin.
- CAD/CAM Computer-assisted design/computer-assisted manufacture.
- CAHI Central Aero and Hydrodynamics Institute of the Russian Federation; also transliterated as TsAGI.
- canards Foreplanes, fixed or controllable aerodynamic surfaces ahead of CG.
- capacity The volume swept out on each stroke by the pistons of a piston engine. It is expressed in cc (cubic centimetres) for small engines and in litres (1 litre = 1,000 cc) for larger ones. Also known as displacement or swept volume.
- carbon fibre Fine filament of carbon/graphite used as strength element in composites.
- CAS (1) Calibrated airspeed, ASI calibrated to allow for air compressibility according to ISA S/L; (2) close air support.
- casevac Casualty evacuation.
- Cat Category. Meanings include runway visibility and decision height minima for ILS.
- CATIA Computer-aided three-dimensional interactive analysis; Anglicised form of French CAD proprietary system (Conception assistée tridimensionelle interactive d'applications).
- CBU Cluster bomb unit.
- CEAM Centre d'Expériences Aériennes Militaires.
- CEAT Centre d'Essais Aéronautiques de Toulouse.
- Ceconite Manmade covering material for light aircraft; trade name.
- CEO Chief executive officer.
- CEV Centre d'Essais en Vol.
- CFE Conventional Forces in Europe.
- CFRP Carbon fibre-reinforced plastics.
- CG Centre of gravity.
- chaff Thin slivers of radar-reflective material cut to length appropriate to wavelengths of hostile radars and scattered in bundles to protect friendly aircraft.
- chord Distance from leading-edge to trailing-edge measured parallel to longitudinal axis.
- CIS Commonwealth of Independent [ex-USSR] States. See also RFAS.
- CKD Component knocked down, for assembly elsewhere.
- clean (1) In flight configuration with landing gear, flaps, slats and so on retracted; (2) Without any optional external stores.
- c/n Constructor's number; manufacturer's serial number.
- C of A Certificate of Airworthiness; awarded to each individual aircraft (compare Type Certificate).
- COIN Counter-insurgency.
- collective pitch Controls pitch of all blades of helicopter main rotor in unison.
- combi Civil aircraft carrying both freight and passengers on main deck.
- comint Communications intelligence.
- composite Material made of two constituents, such as filaments or short whiskers plus adhesive forming binding matrix.
- constant-speed Variable-pitch propeller governed by a CSU so that its rotational speed is held constant.
- contrarotating Propellers on same axis turning in opposite directions (compare C/R).
- conventional and manual Aeroplane manoeuvring surfaces mechanically linked to pilot's hand and foot controls, unassisted (except, optionally, by aerodynamic or mass balances) and comprising ailerons on the outboard wing, rudder(s) to the rear of fixed tailfin(s) and elevators to the rear of a fixed (but optionally, incidence angle trimmable) tailplane. The description optionally includes leading-edge slats, flaps on inboard trailing-edges and trim tabs, all of which are mentioned separately, if installed. Ailerons which droop in unison with flaps (and thus are not the primary means of lowering stalling speed) are regarded as conventional. Control systems not conforming to the above - in that they have foreplanes, one or more all-moving tail surfaces, or flaperons, and those with mechanical/electronic assistance or interception of the pilot's movements - are described in appropriate detail.
- convertible Transport aircraft able to be equipped to carry passengers or cargo, but not both simultaneously.
- COO Chief operating officer.
- core Gas generator portion of turbofan comprising compressor(s), combustion chamber and turbine(s).
- C/R Counter-rotating; propellers of multi-engined aircraft turning in opposite directions on different axes (compare contrarotating).
- CRT Cathode-ray tube.
- cruising speed Flight speed on less than full engine power; maximum is normally at 75%, if not otherwise specified, but some manufacturers use higher throttle settings.
- CSAS Command and stability augmentation system (part of AFCS).
- CTOL Conventional take-off and landing (compare V/STOL).
- CVR Cockpit voice recorder.
- CY Calendar year; 1 January to 31 December. Compare FY.
- cyclic pitch Controls variation of pitch as helicopter rotor blade makes each revolution.
